This invention relates to an apparatus for the on-site generation of polyurethane foam. More particularly, this invention relates to an apparatus of this type having improved means for cleaning the mixing chamber thereof.
Several portable apparatus have been disclosed in the art for the generation of polyurethane foam. See, for example, U.S. Pat. No. 3,178,157, issued to Cole on Apr. 3, 1965; U.S. Pat. No. 3,541,023, which issued Nov. 17, 1970, to Cole; and U.S. Pat. No. 3,769,232, which issued Oct. 30, 1973, to Houldridge. Apparatus of this type usually includes two storage tanks for supplying two inter-reactive polyurethanefoaming materials, means for imposing a gas pressure in these tanks to expell the reactants therefrom and a mixing chamber having an outlet and two valved inlets for mixing the reactants before they are dispensed as a foaming mixture from the mixing chamber. These prior art apparatus permit dispensing of polyurethane foam on site for use in an increasing number of applications, such as making molded foam insulation, furniture parts, structural elements, packaging, and so forth.
It has been found desirable to periodically flush the mixing chamber with a suitable solvent to clean the mixing chamber and remove any material which has accumulated therein. Build-up of material could result in improper mixing, poor flow characteristics, and improper ratio of ingredients, all of which could affect the quality of foam produced.
For the purpose of cleaning the mixing chamber, the apparatus may include a solvent tank which is connected to the mixing chamber to provide a supply of solvent for flushing purposes. Such arrangement is shown, for example, in previusly mentioned U.S. Pat. Nos. 3,769,232 and 3,541,023.
During the flushing operation of previously known apparatus, solvent is expelled onto the floor or ground or into a separate container. This results in a waste of solvent and increased expense. In addition, if the solvent is expelled directly onto the floor or ground it presents an ecological problem as the solvent constitutes a pollutant.
In view of the above, it is an object of the present invention to provide an improved foam generating apparatus wherein the solvent used for flushing the mixing chamber is recovered.
An improved object of the present invention is to provide an improved foam generating apparatus wherein the solvent used for flushing the mixing chamber is recycled.
According to the invention, the apparatus includes first and second reactant storage tanks which are connected to the mixing chamber through mixing chamber inlet valves. A solvent tank is provided having an inlet and an outlet. The solvent tank is connected to a pump which is in turn connected to the mixing chamber through an inlet valve. The tank is so arranged that the discharge from the mixing chamber can be returned to the solvent tank through the inlet thereof and continuous recycling of the solvent through the mixing chamber can take place when desired.